The objective of the research is the development and evaluation of a system called MEDINQUIRY that will allow physicians personal access to patient medical data through natural language queries to support both patient management and clinical research. The system will aid the physician in clinical practice in planning theory and assessing among the various parameters of a disease, in assessing the efficacy of different therapeutic protocols, and, thus, increasing medical understanding of the nature of the disease process. Using the system should lead to better patient care and more effective delivery of health services. A prototype MEDINQUIRY system has been implemented for a small data base on malignant melanoma. The physician can type in queries in English that retrieve specified data for particular patients of four groups of patients, that show relations among given attributes, that perform simple calculations, and that allow him to browse through the data base. The system supports dialog interactions; that is, the user can follow a line of inquiry to test particular hypotheses by entering a sequence of queries that depend on each other in a natural way. The proposed research will extend the capabilities of MEDINQUIRY, establishing it in several clinical environments as an experimental system with an expanded data base on melanoma and with a separate data base on colon carcinoma. Since it is possible for a physician to introduce into the data base higher order concepts that help organize the data, the data base will take on some of the characteristics of knowledge base and thus come to reflect increasingly more of the current state of medical understanding for the disease contained in it. Studies will be made of the use of the system by physicians and of the requirements for adapting the system for more widespread use on different diseases and in other computer facilities.